Mayweather to return on May 5 — but against Pacquiao?

Floyd Mayweather Jr. will make the first defense of the WBC welterweight belt he won by stopping Victor Ortiz last month against an opponent to be determined on May 5 at the MGM Grand in Las Vegas, Mayweather’s adviser, Leonard Ellerbe, confirmed to RingTV.com on Wednesday night.

ESPN.com initially reported the story.

“Floyd is just looking to make the biggest fight out there, and everybody knows what that fight is,” said Ellerbe, referring to THE RING No. 1-rated pound-for-pound Manny Pacquiao (53-3-2, 38 KOs), the current WBO welterweight titleholder.

“Floyd’s always been willing to make the biggest fights that are out there, and that’s what we’ve been doing. Floyd has fought the biggest and the best that are available and the best competition that’s been out there.”

Negotiations for a megabout between Pacquiao, who is promoted by Top Rank Inc., and Mayweather (42-0, 26 KOs), who is handled by Golden Boy Promotions, have failed twice over Mayweather’s insistance on Olympic-style random drug testing.

Prior to his past two victories over Shane Mosley and Ortiz in May of last year and in September, Mayweather required that his opponents undergo Olympic-style random drug testing of urine and blood that was conducted by United States Anti-Doping Agency.

Pacquiao has an ongoing lawsuit against Mayweather, accusing him of defamation and asserting that the fighter has continued to insinuate publicly that Pacquiao’s success over eight weight classes is the result of having used performance-enhancing drugs.

But Top Rank Inc. CEO Bob Arum believes that those details can be worked out.

“That’s not a problem,” said Arum of the lawsuit. “That’s something that could probably get worked out as part of a negotiation.”

What could be a problem, said Arum, are the number of outstanding legal issues pending for Mayweather.

“But the major thing is his criminal legal situation. There’s a lot of serious stuff going on,” said Arum. “He may not be around in May. He can’t go into a fight and then, maybe have to go on trial.”

Mayweather, who turns 35 in February, ended a 16-month layoff when he dethroned Ortiz by fourth-round knockout on Sept. 17.

Prior to that, Mayweather scored a one-sided decision over Mosley. The win over Mosley followed a similarly one-sided unanimous decision rout over current THE RING lightweight champ Juan Manuel Marquez.

Mayweather emerged from a nearly two-year retirement to face Marquez, having previously scored a 10th-round stoppage of Ricky Hatton in December of 2007.

Marquez is preparing for his third bout with Pacquiao on Nov. 12 at the MGM Grand in Las Vegas, having battled Pacquiao through a draw and a split-decision victory in two prior meetings as featherweights and junior lightweights.

“Any opponent that Floyd Mayweather fights, in his whole career, the most money they’ve made has been against Floyd Mayweather,” said Ellerbe.

“But anybody that Floyd Mayweather fights is going to be in the biggest fight that he’s ever going to have been in. Everyone knows what the biggest fight out there in the sport is, and that’s no secret.”